1. Field of the Invention
The present invention relates to a magnetoresistive (MR) effect transducer which can be used as a read head for sensing a leakage magnetic field from a magnetic medium.
2. Description of the Related Art
MR effect transducers are divided into a ferromagnetic tunneling junction (MTJ)-type and a spin value type.
An MTJ structure of the MTJ-type MR effect transducer is constructed by a pinned ferromagnetic layer, a free ferromagnetic layer and a non-magnetic insulating layer sandwiched by the pinned ferromagnetic layer and the free ferromagnetic layer.
On the other hand, a spin valve type MR effect transducer is constructed by a pinned ferromagnetic layer, a free ferromagnetic layer and a non-magnetic conductive layer sandwiched by the pinned ferromagnetic layer and the free ferromagnetic layer.
In a prior art MTJ-type MR effect transducer (see JP-A-10-162327), longitudinal bias ferromagnetic layers are provided at the side of the MTJ structure to provide magnetic domain control over the free ferromagnetic layer, thus suppressing the Barkhausen noise. This will be explained later in detail.
On the other hand, in a prior art spin value type MR effect transducer (see U.S. Pat. No. 5,668,688), longitudinal bias ferromagnetic layers are also provided at the side of the spin value structure to provide magnetic domain control over the free ferromagnetic layer, thus suppressing the Barkhausen noise.
In the above-described prior art MR effect transducers, however, since the free ferromagnetic layer is separated from the longitudinal bias ferromagnetic layer by a magnetic isolation layer, it is difficult to apply a sufficiently large magnetic bias field to the free ferromagnetic layer, which would increase the noise in reproduced signals.
In addition, in the above-described prior art MR effect transducers, each layer of the MTJ or spin value structure has the same pattern. Therefore, when the MTJ or spin value structure is patterned by a milling process, metal particles or contamination may be adhered to the sides of the non-magnetic layer, so that the pinned ferromagnetic layer and the free ferromagnetic layer are short-circuited by the metal particles or contamination adhered to the sides of the non-magnetic layer. This would decrease the manufacturing yield of MR effect transducers.